1. Field of the Invention
This invention relates to a safety device for an oil burner such as an oil-fired space heater, and more particularly to a safety device for an oil burner which is adapted to detect abnormal combustion of fuel oil in the oil burner which forms, in particular, an abnormally decreased flame sufficient to produce incomplete combustion gas.
2. Description of the Prior Art
An oil burner generally has an automatic fire-extinguishing device incorporated therein which serves to rapidly stop combustion of fuel oil in the oil burner when any emergency such as earthquake or the like occurs. Such a fire-extinguishing device is typically activated depending upon an abnormal variation in a combustion temperature of the oil burner detected by means of bimetal or shape memory alloy to carry out fire-extinguishing of the oil burner prior to the abnormal combustion of the oil burner.
Abnormal combustion includes excessively increased combustion which forms an abnormally large flame and excessively decreased combustion which forms an abnormally small flame. The latter abnormal combustion generally is apt to cause a large amount of incomplete combustion gas, accordingly, it is highly desirable to start an automatic fire-extinguishing device prior to the abnormal combustion.
The stopping of the excessively decreased combustion by detecting a combustion temperature of the oil burner as in the excessively increased combustion requires the detection of a decrease in a temperature of the oil burner from the stationary combustion to the abnormal combustion. However, this undesirably detects a low temperature of the oil burner immediately after the ignition as well, to thereby fail to effectively start combustion of the oil burner.
Also, the detection of abnormal combustion in the oil burner requires a temperature sensor or detector to be arranged in proximity to a combustion cylinder of the oil burner. This causes the mechanical and electrical connection between the temperature detector and the fire-extinguishing device to be highly complicated, because the combustion cylinder must be constructed to be operated manually as well as automatically at the time of ignition of the oil burner.